Many per- and polyfluoroalkyl substances (PFAS) are strongly resistant to chemical, physical, and biological degradation. They are relatively difficult to remove from solid samples, such as soil and biosolids. Recent studies have demonstrated that PFAS laden in soil and granular activated carbon (GAC) can be degraded by means of intense heating at elevated temperatures (e.g., 700℃). Building on previous research, the project team aims to develop an innovative catalyst-assisted low-temperature treatment (LCT) method to effectively decompose PFAS present in laboratory-prepared and field-impacted solid samples, including soils, GAC, and biosolids. This limited-scope project will pursue the following four objectives:

1. Identify appropriate catalysts and the key rate-limiting steps/factors of PFAS thermal decomposition;
2. Optimize LCT for practical and effective decomposition of PFAS in aqueous film-forming foams (AFFF) and field-impacted solid samples, including soils, GAC, and biosolids;
3. Characterize decomposition products of PFAS generated during LCT treatments and establish a complete fluorine (F) mass balance; and
4. Investigate the removal and decomposition of co-occurring chemicals (e.g., hydrocarbons) of PFAS by LCT.

The project team will streamline LCT for effective degradation of PFAS in AFFF and solid samples. Key parameters, including catalyst, temperature‒time profile, and solid texture will be investigated and decomposition kinetics (e.g., half-lives), thermodynamics, and pathways of PFAS with different chain lengths and functionalities will be determined. The project team will then optimize LCT processes for field samples collected from “hot spots” of PFAS and evaluate LCT for treatment and degradation of co-occurring chemicals present in AFFF and various solid matrices. Ultrahigh pressure liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and gas chromatography coupled with ion trap tandem mass spectrometry will be employed to identify decomposition products of PFAS generated during LCT treatments. The yield of fluorine (F) ions from PFAS treated by LCT will be determined, and a complete F mass balance on treated matrices entering and exiting LCT will be established.

The treatment approaches (LCT) developed in this research will help to:

• Improve management of PFAS sites by facilitating the establishment of cost-effective and efficient remedial methods for complete destruction of PFAS;
• Identify catalysts and means that can lower the temperature and energy needed for the thermal treatments;
• Create new knowledge on the stability and decomposition mechanisms of various PFAS during these innovative catalyst-based thermal treatments;
• Identify the effect of matrices (e.g., soil properties and co-occurring chemicals); and
• Improve the reliability of treatment processes and expedite the cleanup and closure of Department of Defense impacted sites.

(Anticipated Project Completion - 2025)